Chapter III 

 MORPHOLOGY AND DESCRIPTION 



INTERPRETATION OF PUBLISHED DESCRIPTIONS 



Basic Assumptions: In interpreting the descriptions of Aspergilli in a 

 literature covering a long period of time, certain assumptions, although 

 not always justified, form a working hypothesis for presumptive identi- 

 fication. Conidiophore walls and conidial walls are assumed to be color- 

 less and smooth, unless color or markings are either figured or described. 

 Perithecia and sclerotia are assumed to be lacking unless the presence of 

 such structures is specifically noted. Colors are assumed to apply to the 

 general color scheme of the colony, unless specifically applied to the 

 conidia, ascospores, or other details by the describer. Whereas colony 

 coloration may arise from an admixture of conidial structures and varying 

 amounts of vegetative hyphae, colored or uncolored, together with perithecia 

 or sclerotia in greater or lesser numbers, it is assumed to result from the 

 massing of conidial heads unless otherwise stated. 



Difficulties encountered in interpreting descriptions based upon color 

 are less for the worker with a growing culture before him than for the one 

 handling descriptive literature alone, since the presence of white, green, 

 yellow-green, brown, or black heads is readily distinguished with a handlens, 

 even though sparingly produced upon a colony in which another color 

 predominates as in many members of the A. glaucus group, or in A.fiavipcs. 

 The color of the conidial heads is often made the primary basis of species 

 description. 



Extent of Study: Interpretation of descriptive literature accompanied 

 and supplemented rather than preceded the study of great numbers of 

 cultures so that the groups established are based upon the actual handling 

 of thousands of cultures representing hundreds of forms of Aspergillus 

 handled during a period of more than thirty years. Many of these were 

 studied on natural substrata before their isolation. In addition, exami- 

 nation of exsiccati from several large herbaria, while more or less unsatisfac- 

 tory as to detail in identification of species, furnish confirmatory evidence 

 of the soundness of the groupings proposed. 



Types: For a few of the specific names in use today, the type strain has 

 been definitely maintained in culture. For most series, selection of a 

 morphological entity to give a concrete concept back of the use of a name 

 becomes a matter of critical judgment. For the purposes of this manual, 

 an attempt has been made to base the use of the individual name upon the 



10 



